Method for bringing two stationary gearwheels into engagement with one another on a lapping or testing machine

ABSTRACT

A method for bringing into engagement two gearwheels on a lapping or testing machine. The gearwheels are displaced towards one another until they come into mutual contact and in the event of the tips of two teeth contacting one gearwheel is rotated through a fraction of the tooth pitch and engagement of the two gearwheels is prevented until a tooth of one gearwheel is opposite a gap in the other gearwheel.

O United States Patent 11113,579,803

[72] Inventor Alfred Johann Lautenschlager [50] Field of Search 29/434, Zurich, Switzerland 159.2; 74/388, 406; 51/287; 90/l.6 [2]] Appl. No. 737,789 22 Filed June 13 19 3 [56] References Cited Division of Ser. No. 612,378, Jan. 30, 1967, UNITED STATES PATENTS $193,403,561 2,150,313 3/1939 Bauer 5 l/287X Patented 5, 1971 2,947,120 8/1960 Bauer et a1 5 l/287X 1 Asslgnee oerPkon-Buhrie Holding AG 2,984,956 5/1961 Schicht 51/287 Zurich, Switzerland 3,099,901 8/1963 Hunkeler 5 l/287X 1 Pflomy eb. 1, 1966 3,263,568 8/1966 Kretzschmar et al 90/1.6 [33 Switzerland [31 1394/66 Primary ExammerJohn F. Campbell Assistant ExaminerV1ct0r A. D1Palma Attorney-Wenderoth, Lind & Ponack [54] METHOD FOR BRINGING TWO STATIONARY GEARWHEELS INTO ENGAGEMENT WITH oNE ABSTEAICE A h g f ANOTHER 0N ALAPPING 0R TESTING MACHINE 1 s a agpmg tesgmg i e Beam 9 Claims, 7 Drawing Figs are 1sp aced towar s one anot er unt1 t ey come mto niutua contact and 1n the event of the tips of two teeth contactmg one [52] [1.8. CI 29/434, gearwhee] is rotated through a fraction of the tooth pitch and 29/ 1 59.2, 51/287 engagement of the two gearwheels is prevented until a tooth of [5 Int. Cl. 823p 19/00 one gearwheel is opposite a gap in the other gearwheel.

PATENIEU HAYZS IQYI SHEET 1 [1F 4 INVENTOR H63 ALFRED JOHANN LAUTENSCHLAGER PATENTEU W2 5 IHYI SHEET 2 (IF 4 FIGA INVENTOR ALFRED JOHANN LAUTENSCHLAGER BY m ATTORNEYB PATENTED HAY25 |97l SHEET 3 OF 4 INVENTOR ALFRED JOHANN LAUT'ENscHLAcER PATENTEUHAYZSISTI 3,579,803

ALFRED JOHANN L AUT EN SCHLAGER BY Ya M ATTOR NEYS METHOD FOR BRINGING TWO STATIONARY GEARWHEELS INTO ENGAGEMENT WITH ONE ANOTHER ON A LAPPING OR TESTING MACHINE This application is a Division of application Ser. No. 612,378 filed Jan. 30, 1967, now US. Pat. No. 3,403,569, Oct. l, 1968 entitled Apparatus for Bringing Two Stationary Gearwheels into Engagement With One Another On a Lapping Or Testing Machine.

The invention relates to a method-of bringing two stationary gearwheels into engagement with one another on a lapping or testing machine, wherein the two gearwheels are moved towards one another, turned relatively to one another and in the event of the tip of one tooth on one gearwheel coming opposite a gap in the other gearwheel, brought into engagement with one another by being advanced. The invention further relates to a device for carrying out the method.

In lapping machines, it is known to bring two gearwheels which are to be lapped into engagement with one another, step by step, because there is a high probability that, in the event of direct advance, the tip of a tooth on the one gearwheel will strike against the tip of a tooth on the other gearwheel. With this step-bystep procedure, the two gearwheels at first approach with a rapid motion to a distance of a few millimeters apart, then one of the two gearwheels is turned by hand untilthe tip of a tooth on the one gearwheel is opposite a gap in the other gearwheel, whereupon the gearwheels are brought into engagement with one another.

Furthermore, a device is known whereby the two gearwheels to be brought into engagement with one another are first aligned in relation to one another (see US. Pat. No. 2,150,313). In this device, a pivoted lever is provided which, before the gearwheels are driven towards one another, is pressed against the gearwheels in the course of which a ball detent on the lever is pressed into a gap in one gearwheel while at the same time a sharp-edged dog on the lever engages in a gap in an adjusting wheel which is provided with sharpedged teeth and which is rigidly connected to the second gearwheel. As a result of this swivel movement of the lever, the two gearwheels to be brought into engagement with one another are alignedin relation to one another so that they are sure to come into engagement with one another when advanced.

These two known methods of bringing two gearwheels into engagement with one another require the presence of an operator and are time consuming and inconvenient. In the method first mentioned, the operator must take care each time to ensure that the tip of a tooth on the one gearwheel is in fact opposite a gap in the teeth on the other gearwheel. The other method is even more inconvenient for lapping machines because the operator first has to ensure, when securing the one gearwheel in position, that it is in the correct position with respect to the adjusting wheel. Then, during the swiveling of the lever, the operator has to ensure that the ball detent does in fact enter a gap in the other gearwheel.

It is an object of the invention to overcome these disadvantages and to provide a method which can also be used for gearwheels which are not accessible or visible to an operator and which can be carried out-easily and automatically by a device without the presence of an operator.

A further object is to provide a construction wherein the gearwheels are moved towards one another until they come into mutual contact and, in the event of mutual contact between the heads of two teeth, one gearwheel is turned through a fraction of the tooth pitch and entrainment of the second gearwheel by the first-mentioned gearwheel is prevented until a tooth in one gearwheel is opposite a gap in the other gearwheel.

In a preferred example of the method, entrainment of one gearwheel by the other gearwheel can be prevented by the mutual contact between the two gearwheels being discontinued again by withdrawal of one gearwheel.

In another example of the method, entrainment of the one gearwheel by the other gearwheel can be prevented by braking the first-mentioned gearwheel, and the second gearwheel can be pressed against the first gearwheel and, at the same time, turned in relation to the first gearwheel until a tooth in one gearwheel engages in a gap in the other gearwheel.

A further object is to provide a device for carrying out the method on a lapping machine or testing machine with a servomechanism which comprises a stop adapted for automatic displacement, for the displacement of one gearwheel towards the other gearwheel, so that an inching control mechanism M is provided in order to turn one of the two gearwheels through a fraction of the tooth pitch.

In a preferred embodiment of the device, the servomechanism may comprise a switch member which, in the case of mutual contact between the tips of two teeth, discontinues the contact again. The inching control mechanism maycomprise a rolling segment which has a friction lining and is displaceable in its longitudinal direction by means of a first working cylinder with a piston so as to come into engagement with a pulley driving the one gearwheel, and which is dis placeable transversely to said longitudinal direction by means of a second working cylinder with a piston in order to rotate the pulley and hence the gearwheel by a fraction of the tooth pitch.

Two examples of carrying out the method according to the invention are described in detail below with reference to the accompanying drawings in which a single embodiment of the device according to the invention is illustrated and in which:

FIG. 1 is a perspective illustration of two hypoid-toothed bevel wheels in which the tips of two teeth are striking one against the other;

. FIG. 2 is a perspective illustration of the same two gearwheels in engagement;

FIG. 3 is a plan view of a lapping machine with the device for bringing two gearwheels, to be lapped on the machine, into engagement with one another;

FIG. 4 shows a section on the line IV-IV in FIG. 3 with the servomechanism whereby the two gearwheels to be lapped together are displaceable towards and away from one another, with a slide in its initial position;

FIG. 5 shows a section on the line V-V in FIG. 3 with an inching control mechanism to turn one of the two gearwheels through a fraction of its tooth pitch;

FIG. 6 is an electric wiring diagram for a first example of the method with the contacts in a position corresponding to the initial position shown in FIG. 4 and FIG. 7 is an electric wiring diagram for a second example of an embodiment with the contacts in the initial position corresponding to FIG. 4.

According to FIGS. 3 and 5, a spindle slide 11 is mounted for displacement in guides I2 on a bed 10. A spindle 13 is mounted for rotation on this slide 11. Secured to one end of this spindle 13 is a belt pulley 14 which is in driving connection with a motor 16 through two belts 15. This motor 16 serves to drive the spindle 13 during the lapping operation. One of the two gearwheels I7, 18 to be lapped together is fixed to the other end of the spindle 13. Further secured to the bed 10 is a spindle housing 19 in which a second spindle 20 is mounted for rotation. The other of the two gearwheels 17, 18 to be lapped together is fixed to this second spindle 20.

As shown in FIG. 4, a housing 21 is secured to the spindle slide 11. In this housing 21 there is a piston 22 which is rigidly connected to the bed 10 through a piston rod 23. Also in the housing 21 is a copying valve piston 24 which is connected to a valve magnet 25. The energized valve magnet 25 tends to urge the valve piston 24 into its right-hand end position. If the valve magnet is deenergized, the spring 26 tends to urge the valve piston 24 into the left-hand end position. When the slide 11 is in the initial position, the valve piston 24 is held at its lefthand end in its neutral position by a stop on the housing 10.

When the valve piston 24 is in the right-hand end position, a hydraulic pipeline 27 is in communication with a chamber 28 at the right-hand side of the piston 22. When the valve piston 24 is in the left-hand end position, on the other hand, the hydraulic pipeline 27 is in communication with a chamber 29 at the left-hand side of the piston 22. If the chamber 28 at the right-hand side is in communication with the hydraulic pipeline 27 the chamber 29 at the left-hand side of the piston 22 is in communication with a discharge pipeline 30 and conversely, if the chamber 29 atthe left-hand side of the piston 22 is in communication with the pressure line 27, the chamber 28 at the right-hand side of the piston 22 is in communication with the discharge pipeline 30.

When the right-hand chamber 28 is in communication with the pressure line 27, the slide 1 1 is displaced towards the right and, conversely, when the left-hand chamber is in communication with the pressure line, the slide 11 is displaced towards the left. Thus a displacement of the valve piston 24 towards the right likewise causes a movement of the slide 11 towards the right and conversely a displacement of the valve piston 24 towards the left likewise causes a displacement of the slide 11 towards the left. The mechanism described is termed a servomechanism.

Further secured to the bed is a limit switch 31 which can be actuated by the slide 11 in the left-hand end position. Two limit switches 32 and 33 which can be actuated by the valve piston 24 are secured to the housing 21. These electrical switches are described in detail below.

A stop slide 34 is further mounted for displacement on the bed 10. A spindle 35, to the left-hand end of which there is secured a handwheel 36, is provided for the displacement of this stop slide 34. At its left-hand end, this spindle is also mounted for rotation in the bed 10 and secured against axial displacement, while the right-hand end of the spindle 35 comprises a thread 37 and is screwed into an extension 38 on the slide 34.

By turning the handwheel 36, the slide 34 can be displaced towards the right or left with respect to the bed 10. A stop 39 is mounted for displacement on the slide 34. A spindle 40, to the right-hand end of which there is secured a worm wheel 41, is provided for the displacement of this stop 39. The spindle 40 is mounted for rotation on the stop slide 34 and held against axial displacement. The spindle 40 is threaded and is screwed into an extension 39 on the stop 39.

The worm wheel 41 is in engagement with a worm 42 which is secured to a motor 43 which in turn is secured to the stop slide 34. The stop 39 has a cam 44 for the actuation of two electric switches 45 and 46, of which the limit switch 46 comprises a break contact 46.] and a make contact 46.2 (see FIG. 6) which are described below. The stop 39 is in the path of the valve piston 24.

According to FIG. 5, an inching control mechanism is mounted on the spindle slide 11. This inching control mechanism comprises a controlling segment 50 which is provided with a friction lining 51 and which is articulated to one arm of a two-armed lever 53 for pivoting by means of a pin 52. This lever 53 is mounted for pivoting on a pin 54 secured to the slide 11. The other arm of the lever 53 is pressed, by means of a spring 55, against a piston 56 which is mounted for displacement in a housing 57. At the right-hand side of the piston 56, a cylinder compartment 58 is in communication with a valve 60 through a pipeline 59. A pressure line 61 and a discharge line 62 are connected to this valve 60.

A further piston 63, which is likewise mounted for displacement in the housing 57, is provided for the actuation of the rolling segment 50. A sliding block 64, which is guided for displacement in a slot in the rolling segment 50, is pivotally mounted on the piston 63. The piston 63 further comprises an annular stop 65. A spring 66, which bears on the one hand against the stop 65 and on the other hand against a frame 67 secured to the slide 11, tends to urge the piston 63 into its lower position. .This lower position of the piston 63 is adjustable by means of screwed-on adjusting nuts 68.

A cylinder compartment 69 below the piston 63 is in communication with the pipeline 59 through a throttle valve 70. Further secured to the frame 67, through a holder 71, is a limit switch 72 which is adapted for actuation by the piston 63 in its uppermost position. Secured to the valve 60, is a valve magnet 73 which is connected to a valve piston 74. When the valve magnet 73 is energized, the valve piston 74 is in its lowest posi tion and the pressure line 61 is in communication, through the line 59, with the cylinder compartments 58 and 69. If the valve magnet 73 is deenergized, on the other hand, then the valve piston 74 is in its uppennost position, under the action of a spring 75, and the cylinder compartments 58 and 69 are connected to the discharge line 62 through line 59.

Secured to the spindle housing 19 is a brake whereby the spindle 20 can be held against rotation as a result of which, entrainment of the one gearwheel on rotation of the other gearwheel is prevented if the tips of two teeth on the two gearwheels are in contact. The brake 80 comprises a brake disc 81 as well as a lever 82 which is mounted for pivoting on a pin 83 and is provided with a brake lining 84. A spring 85 tends to pivot the lever 82 in clockwise direction. In the energized state, a magnet 86 causes the brake lining 84 to be pressed against the brake disc 81. According to FIG. 6, a start button 90 and a stop button 91 are connected in series with a relay 92 through an adapting transformer 93. The relay 92 is further connected to a self-holding contact 92.] in order to prevent the circuit from being interrupted on release of the start button 90. The relay 92 is further connected to a contact 92.2 which is connected, in series with the copying valve magnet 25, to a direct-current source 94 which in turn is connected to the adapting transformer 93. On actuation of the starting button 90, the copying valve 25 is thus actuated immediately.

As can be seen from FIG. 6, the motor 43 described above rotates in the one direction when the three contacts 95.3 are closed by a relay 95 and in the other direction when the three contacts 96.2 are closed by a further relay 96. The relay 95 is connected in series with the limit switches 31 and 45, which are constructed in the form of break contacts, and with the limit switch 32 which is constructed in the form of a make contact. Furthermore, three further relay contacts 97.1, 92.3 and 96.1 are connected in series with the relay 95. A self-holding contact 95.1 prevents the circuit from being interrupted on release of the make contact 32. In order that the motor 43 may rotate in the one direction, the make contact 32 must be actuated while at the same time, both the break contact 31 and the break contact 45 must not be actuated and the two relays 97 and 96 must be deenergized, while the relay 92 must be energized.

The relay 96 is connected in series with the limit switches constructed in the fonn of a make contact 33 and break contact 46.1, which are connected in parallel with one another. Furthermore, the relay 96 is connected in series with the relay contacts 92.4 and 97.2 which are likewise connected in parallel with one another. Thus in order that the motor may be able to rotate in the other direction, the break contact 46.1 must be released and furthermore, one of the two relay contacts 91.4 and 97.2 must be closed, and finally the relay contact 95.2 must be closed.

The magnet 73 is connected in series with the make contact 46.2 and the relay contact 97.4. In order to energize the magnet 73, therefore, the make contact 46.2 must be actuated, but the relay 97 must be energized. This relay is connected in series with the break contact 72, however, so that on actuation of the switch 72, the valve magnet 73 is deenergized.

As shown in FIG. 7, a start button 90 and a stop button 91 are connected in series with a relay 92 to an adapting transformer 93. The relay 92 is connected to a self-holding contact 92.1 in order to prevent the circuit from being interrupted on release of the start button 90. The relay 92 is further connected to a contact 92.2 which is connected, in series with the copying valve magnet 25, to a direct-current source 94, which in turn is connected to the adapting transformer 93. On actuation of the start button 90, the magnet 25 of the copying valve is energized immediately.

As can further be seen from FIG. 7, the inching motor 43, as in the wiring diagram shown in FIG. 6, turns in the one direction when the three contacts 95.3 are closed through a relay 95 and in the other direction when the three contacts 96.2 are closed through a further relay 96. The relay 95 is connected in series with limit switches 31 and 45 constructed in the fonn of break contacts and with the limit switch 32 constructed in the form of a make contact.

Furthermore, a break contact 33.1 is connected in series with the relay 95. This break contact 33.1 is connected to the make contact 33.2 which is connected in series with the relay 97. The break contact 33.1 and the make contact 33.2 are actuated jointly through the limit switch 33 (FIG. 4). In addition, the two relay contacts 92.3 and 96.1 are connected in series with the relay 95. A self-holding contact 95.1 prevents the circuit from being interrupted on release of the make contact 32.

Thus, in order that the inching motor 43 may rotate in the one direction, the make contact 32 must be actuated and at the same time neither the break contact 31 nor the break contact 45 must be actuated. The relay 92 must be energized and the relay 96 must be deenergized. The relays 97 and 96 are connected in parallel with one another and in series with the break contact 46.

Furthermore, the relay 97 is connected in series with the make contact 33.2 and the time-relay contact 98.1 and in parallel with the time relay 98 which in turn is connected in series with the make contact 72. The relay 97 is connected to the relay contact 97.1 which is connected in series with the magnets 73 and 86 connected in parallel with one another. Thus when the relay 97 is energized, the inching control mechanism and the brake 80 are actuated at the same time. Finally, the relay 96 is connected in series with the relay contacts 92.4 and 95.2. The inching motor 43 runs backwards when the end switch 46 is not actuated and the relays 92 and 95 are deenergized.

According to a first example, the mode of operation of the device described is as follows:

As soon as two gearwheels 17, 18 to be lapped with one another have been fixed to the two spindles 13 and 20, the device is switched on by means of the start button 90. The valve magnet 25 is energized as a result of which the valve piston 24 in FIG. 4 is displaced towards the right so that the pressure line 27 is in communication with the right-hand cylinder compartment 28 and the slide 11 is displaced with a rapid motion towards the right.

In the course of this, the valve piston 24 actuates the make contact 33. The actuation of this make contact 33 does not have any further consequences, however, because the break contact 46.1 connected in parallel with the contact 33 is pressed by the stop 39. The inching motor 43 is therefore neither switched on nor off through this actuation of the make contact 33. The slide 11 is displaced towards the right with a rapid motion until the valve piston 24 strikes against the stop 39.

The stop 39 displaces the valve piston 24 towards the left until the connection between the pressure line 27 and the cylinder compartment 28 is interrupted and the slide 11 stops. The make contact 32 is actuated through the displacement of the valve piston towards the left. As can be seen from FIGS. 4 and 6, the inching motor 43 is switched on because the break contact 45 is closed and the break contact 32 is likewise closed through the displacement of the slide 11. The relay contact 92.3 is likewise closed because the relay 92 was energized on actuation of the start button 90. The relay contacts 97.1 and 96.1 are likewise closed because neither the relay 97 not the relay 96 was energized through switches 46 and 33 as explained above.

The inching motor 43 turns the spindle 40 through the worm gear 42, 41 so that the stop 39 is displaced towards the right. The valve piston 24 which bears against the stop 39 participates in this movement and causes the slide 11 to inch towards the right. If the tips of two teeth on the gearwheels 17 and I8 strike against one another during this movement of the slide 11, as illustrated in FIG. I, the spindle slide 11 stops. A pressure-relief valve, not illustrated in the drawing, prevents excessive forces from arising during this impact between the tips of the teeth.

The valve piston 24 now follows the stop 39 alone and is displaced towards the housing .21 until the make contact 33 is pressed and the relay 97 is closed through the contacts 46.1 and 72. The relay contact 97.1 opens and the inching motor 43 stops. Since the break contact 46.1 is not depressed in this position of the stop 39, and the relay contact 95.2 was closed on the stopping of the motor 43 and deenergizing of the relay 95, the relay 96 is now energized and the inching motor 43 rotates in the opposite direction so that the stop 39 is also displaced in the opposite direction, that is to say towards the left, as a result of which the slide 11 is also displaced towards the left, through the valve piston 24, until the contact between the tips of the teeth is interrupted.

The stop 39 is displaced towards the left until the cam 44 on the stop 39 actuates the switch 46 again. The actuation of the switch 46 has the effect, on the one hand that the motor 43 stops, since the break contact 46.1 (FIG. 6) is interrupted, and, on the other hand, that the valve magnet 73 is energized, because the make contact 46.2 closes at the same time. As a result of the energizing of the valve magnet 73, the valve piston 74 is driven downwards against the action of the spring 75, so that the cylinder compartments 58 and 69 are connected to the pressure line 61 through the pipeline 59. The piston 56 is displaced towards the left, against the force of the spring 55, and urges the rolling segment against the pulley 76.

Through the constriction 70, the piston 63 is displaced upwards-with some delay-against the force of the spring 66, as a result of which the rolling segment is pivoted and causes rotation of the pulley 76. The rotation of the pulley 76 corresponds to a fraction of the tooth pitch of the gearwheel fitted to the spindle 13. When the piston 63 is in the upper most position, the break contact 72 is actuated. As a. result, the relay 97 is deenergized and the relay contact 97.4 opens so that the valve magnet 73 is likewise deenergized. Under the action of the spring 75, the valve piston 74 returns to its uppermost position, as a result of which the cylinder compartments 58 and 69 are connected to the discharge line 62 through the pipeline 59. Under the action of the springs 55 and 66, the pistons 56 and 63 are restored to their initial position, while the piston 56 and the piston 63 return to their initial position again under that action of the constriction 70.

Since the relay 97 was deenergized through the actuation of the switch 72, the relay contact 97.1 (FIG. 6) has closed, as a result of which the relay is energized and the inching motor 43 is switched on so that the stop 39 is again displaced towards the right as a result of which the slide 11 also travels towards the right. If the tip of a tooth on the one gearwheel is not opposite a gap on the other gearwheel, the slide 11 can be displaced towards the right until the two gearwheels are in en gagement and touching one another. The stop 39 continues to move towards the right until the cam 44 strikes against the limit switch 45 and the motor 43 is switched off, as a result of which the stop 39 stops. If the tips of two teeth still strike against one another on the second displacement of the slide 11, the operation described is repeated.

As soon as the gearwheels are in engagement, the lapping operation begins. At the end of the lapping operation, the stop button 91 is actuated, the relay 92 is deenergized and the slide 11 reaches its initial position. If the tip of a tooth on the one gear wheel is already opposite a gap in the other gearwheel on the first displacement of the slide towards the right, the two gearwheels come into engagement with one another immediately without any rotation of the one gearwheel being necessary.

According to a second example, the mode of operation of the device described is as follows:

As soon as two gearwheels 17, 18 to be lapped together are fixed to the two spindles 13 and 20, the device is switched on by means of the start button 90. In the course of this, the relay 92 (FIG. 7) is energized and the relay contact 92.2 closes as a result of which the valve magnet 25 is energized. The second time, the self-holding contact 92.1 closes so that the device does not stop again on the release of the start button 90. The energized valve magnet 25 then displaces the valve piston 24 towards the right so that the pressure line 27 is brought into communication with the right-hand cylinder compartment 28 and the slide 11 is displaced towards the right with a rapid motion.

The valve piston 24 actuates the break contact 33.1 and the make contact 33.2. The actuation of these two contacts 33.1 and 33.2 does not have any further consequences, however, because the break contact 46 which is connected in series is still depressed by the stop 39 and the make contact 32 is opened. The inching motor 43 is therefore neither switched on nor off through this actuation of the break contact 33.1. The slide 11 is displaced with a rapid motion towards the right until I the valve piston 24 strikes against the stop 39. The stop displaces the valve piston 24 towards the left until the communication between the pressure line 27 and the cylinder compartment 28 is interrupted and the slide 11 stops. Through the displacement of the valve piston 24 towards the left, the made contact 32 is actuated.

As can be seen from FIGS. 4 and 7, the inching motor 43 is switched on, because the break contact 45 is closed, the break contact 31 was likewise closed through the displacement of the slide 11; the relay contact 92.3 is likewise closed because the relay 92 was energized on actuation of the start button 90. Furthermore, the relay contact 96.1 is closed because the relay 96 was not energized through the switch 33.2, and finally the break contact 33.1 is closed because the valve piston does not actuate the switch 33. The inching motor 43 turns the spindle 40 through the worm gear 42, 41 so that the stop 39 is displaced towards the right. The valve piston 24, which bears against the stop 39, participates in this movement and causes the slide 11 to be displaced towards the right with an inching motion.

If the tips of two teeth on the gearwheels 17 and 18 strike against one another during this displacement of the slide 1 1, as illustrated in FIG. 1, then the spindle slide 11 stops. A pressure-relief valve not illustrated in the drawing, prevents inadmissibly heavy forces from arising on this impact between the tips of the teeth. The valve piston 24 alone continues to follow the stop 39 and is displaced towards the housing 21 until the make contact 32 is no longer depressed. The inching motor 43 continues to rotate because the contact 32 is bridged by the relay contact 95.1. The operations described so far are substantially similar to the corresponding operations in the first example. Instead of the gearwheels which are in contact being moved apart'from one another again, as in the first example, however, in this second example, the gearwheels are turned relatively to one another; this is effected as follows:

As soon as the valve piston 24 releases the make contact 32 and instead actuates the break contact 33.1 and the make contact 33.2, the relay 97 is energized and the inching motor 43 is stopped because the break contact 46 has already been released by the displacement of the stop 39 and the time switch 98.1 is closed. The relay contact 97.1 is closed and the magnets 73 and 86 are energized through the energized relay 97. The inching control mechanism is actuated in the manner described.

The brake 80 is likewise applied through the magnet 86 so that the gearwheel 18 cannot also rotate. As soon as the gearwheel has been turned so far that one tooth thereof can penetrate into a gap in the other gearwheel, the slide 11 is displaced further towards the right because the stop 39 has been displaced towards the right in the meantime and the servo valve tends to displace the slide 11 towards the right. As a result of this displacement of the slide 11, during which the gearwheels come into engagement with one another, the limit switch 33 becomes free again and the circuit for relay 95 is closed again, the motor 43 starts up again and is finally stopped through actuation of the switch 45.

If the stroke of the piston 63 is not sufiicient for the rotation of the one gearwheel, the limit switch 72 is pressed shortly before the end of its stroke and the time relay 98 is switched on as a result. The contact 98.1 of this relay 98 is opened in the course of this, as a result of which the relay 97 becomes deenergized and so the magnets 73 and 86 are also deenergized through the relay contact 97.1. The piston 63 is displaced into its initial position. The limit switch 72 is no longer actuated. When the time set at the time relay has expired, the contact 98.1 closes. The relay 97 responds again and the magnets 73 and 86 are reenergized and the rotation of the one gearwheel is continued.

A fine stop motor, known per se, may be used instead of the inching control mechanism illustrated in FIG. 5 to rotate the one gearwheel and may serve as a main drive motor for the lapping operation at the same time.

As a result of the deenergizing of the relay 92, the relay contact 92.4 is closed. Since the .stop 39 is in its right-hand end position, the contact 46 is also closed, and since the relay is not energized, the relay contact 95.2 is also closed; thus the relay 96 is energized and the inching motor 43 restores the stop 39 to its initial position. The operation is completed. Since the relay 92 is deenergized, the magnet 25 also deenergized and the slide 11 regains its initial position.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the process, form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the forms hereinbefore described and illustrated in the drawings being merely preferred embodiments thereof.

Iclaim:

1. A process for engaging a first gearwheel with a second gearwheel comprising moving said first gearwheel against said second gearwheel, then upon contact of the tips of the teeth of said gearwheels rotating said first gearwheel relative to said second gearwheel until one tooth of said first gearwheel is opposite a gap between the teeth of the second gearwheel at the same time preventing rotation of said second gearwheel so as not to be taken along by said first gearwheel and then bringing the two wheels in engagement with one another.

2. A method of bringing two gearwheels into engagement with one another, wherein the two gearwheels are displaced towards one another, and, in the event of the tip of a tooth on the one gearwheel coming opposite a gap in the other gearwheel, are brought into engagement with one another by displacing said gearwheels towards one another until they come into mutual contact, and in the event of mutual contact between the tips of two teeth, one gearwheel is rotated through a fraction of the tooth pitch and entrainment of the other gearwheel by said first-mentioned gearwheel is prevented until one tooth of one gearwheel is opposite a gap in the other gearwheel and then bringing the two wheels in engagement with one another.

3. A method as claimed in claim 2 wherein entrainment of one gearwheel by the other gearwheel by the mutual contact between the two gearwheels is prevented by withdrawal of one gearwheel.

4. A method as claimed in claim 3 wherein the withdrawal of one gearwheel and the rotation of the other gearwheel through a fraction of the tooth pitch and the subsequent advance towards one another is repeated until a tooth on one gearwheel engages in a gap in the other gearwheel.

5. A method as claimed in claim 2 wherein entrainment of one gearwheel by the other gearwheel is prevented by braking of said first-mentioned wheel and the other gearwheel is pressed against said first gearwheel and at the same time turned in relation to said first gearwheel until a tooth on the one gearwheel engages in a gap in the other gearwheel.

6. A method as claimed in claim 3 wherein in the event of mutual contact between the tips of two teeth, as a result of which the movement of the two gearwheels towards one another is prematurely interrupted, this premature interruption is used to initiate the rotation of one gearwheel through a fraction of the tooth pitch and to prevent entrainment of the second gearwheel by said first gearwheel.

7. A method as claimed in claim 6 wherein said movement between said two gearwheels is used to initiate the withdrawal of one gearwheel by means of an actuated switch.

8. A method as claimed in claim 6 wherein said movement 9. A method as claimed in claim 6 wherein an infinitely varibetween said two gearwheels actuates a switchto initiate the able inching control mechanism is used for the rotation of one securing of one ge'arwheel against rotation and the rotation of gearwheel with respect to the other gearwheel through a fracthe other gearwheel. tion of the tooth pitch. 

1. A process for engaging a first gearwheel with a second gearwheel comprising moving said first gearwheel against said second gearwheel, then upon contact of the tips of the teeth of said gearwheels rotating said first gearwheel relative to said second gearwheel until one tooth of said first gearwheel is opposite a gap between the teeth of the second gearwheel at the same time preventing rotation of said second gearwheel so as not to be taken along by said first gearwheel and then bringing the two wheels in engagement with one another.
 2. A method of bringing two gearwheels into engagement with one another, wherein the two gearwheels are displaced towards one another, and, in the event of the tip of a tooth on the one gearwheel coming opposite a gap in the other gearwheel, are brought into engagement with one another by displacing said gearwheels towards one another until they come into mutual contact, and in the event of mutual contact between the tips of two teeth, one gearwheel is rotated through a fraction of the tooth pitch and entrainment of the other gearwheel by said first-mentioned gearwheel is prevented until one tooth of one gearwheel is opposite a gap in the other gearwheel and then bringing the two wheels in engagement with one another.
 3. A method as claimed in claim 2 wherein entrainment of one gearwheel by the other gearwheel by the mutual contact between the two gearwheels is prevented by withdrawal of one gearwheel.
 4. A method as claimed in claim 3 wherein the withdrawal of one gearwheel and the rotation of the other gearwheel through a fraction of the tooth pitch and the subsequent advance towards one another is repeated until a tooth on one gearwheel engages in a gap in the other gearwheel.
 5. A method as claimed in claim 2 wherein entrainment of one gearwheel by the other gearwheel is prevented by braking of said first-mentioned wheel and the other gearwheel is pressed against said first gearwheel and at the same time turned in relation to said first gearwheel until a tooth on the one gearwheel engages in a gap in the other gearwheel.
 6. A method as claimed in claim 3 wherein in the event of mutual contact between the tips of two teeth, as a result of which the movement of the two gearwheels towards one another is prematurely interrupted, this premature interruption is used to initiate the rotation of one gearwheel through a fraction of the tooth pitch and to prevent entrainment of the second gearwheel by said first gearwheel.
 7. A method as claimed in claim 6 wherein said movement between said two gearwheels is used to initiate the withdrawal of one gearwheel by means of an actuated switch.
 8. A method as claimed in claim 6 wherein said movement between said two gearwheels actuates a switch to initiate the securing of one gearwheel against rotation and the rotation of the other gearwheel.
 9. A method as claimed in claim 6 wherein an infinitely variable inching control mechanism is used for the rotation of one gearwheel with respect to the other gearwheel through a fraction of the tooth pitch. 